Neural dynamics of predictive timing and motor engagement in music listening

Why do humans spontaneously dance to music? To test the hypothesis that motor dynamics reflect predictive timing during music listening, we created melodies with varying degrees of rhythmic predictability (syncopation) and asked participants to rate their wanting-to-move (groove) experience. Degree of syncopation and groove ratings are quadratically correlated. Magnetoencephalography data showed that, while auditory regions track the rhythm of melodies, beat-related 2-hertz activity and neural dynamics at delta (1.4 hertz) and beta (20 to 30 hertz) rates in the dorsal auditory pathway code for the experience of groove. Critically, the left sensorimotor cortex coordinates these groove-related delta and beta activities. These findings align with the predictions of a neurodynamic model, suggesting that oscillatory motor engagement during music listening reflects predictive timing and is effected by interaction of neural dynamics along the dorsal auditory pathway.


Supplementary Results
Modelling the relation between groove ratings and degree of syncopation.We fitted at the individual level the relation between groove ratings and degree of syncopation.We fitted both a linear and quadratic model, and compared their goodness-of-fit, by using the adjusted r-squared values.For the online experiment (n = 66), we obtained an average adjusted r-squared of 0.14 and 0.37 across melodies, for the linear and quadratic functions.The quadratic model significantly outperformed the linear one (t(65) = 13.1;p < 0.001).For the MEG experiment (n = 29), we obtained an average adjusted r-squared of 0.21 and 0.49 across melodies, for the linear and quadratic functions.The quadratic model significantly outperformed the linear one (t(28) = 11.8;p < 0.001).At the group level, the inverse U-shape profile is very well approximated with a quadratic function for both the online (adjusted r 2 (33) = 0.73) and MEG (adjusted r 2 (33) = 0.67) experiments.

Figure S1 .
Figure S1.Neurodynamic model.(a) Inter-melody correlation between the time-averaged 2 Hz amplitude of each layer of the neurodynamical model (1 to 3; lines, y-axes), as a function of 4 paradigmatic variables (2 Hz acoustic, degree of syncopation, MEG groove ratings, or online groove ratings; columns, x-axes).Data were approximated with a linear function.Pearson's r-squared is reported.Strongest correlations are highlighted with red rectangles.(b) Amplitude of the time-averaged 2 Hz oscillations in the three network layers, in response to each of the 36 melodies, for each condition (low, medium, high).Shades of gray indicate the conditions.Individual points indicate melodies (n = 36).

Figure S2 .
Figure S2.Dominant frequency across the brain volume in the three melodic conditions (low, medium, high).Frequency range 1-45 Hz (after removal of the 1/f decay of the neural power spectrum).(a) For each condition, data were approximated at the group-level with a polynomial function, independently for each dimension (X, Y, Z) of the MNI space.(b) Comparison of the quality of fits (r 2 ), estimated at the individual level, of the 36 melodies grouped per condition (low, medium, high) and plotted for each dimension (Y, X, Z) of the MNI space.

Figure S3 .
Figure S3.MEG experiment: Spectral coding of degree of syncopation and groove ratings in the regions-ofinterest.Spectrum of neural coding of the degree of syncopation (blue) and groove ratings (blue), for each of the regions-of-interest (Fig.4c).Red and blue horizontal lines indicate frequencies with significant coding values (q < 0.005, FDR-corrected).The black line indicates frequencies with significant differences in coding precision between degree of syncopation and groove ratings (q < 0.05, FDR-corrected).Error bars indicate SEM.Inset brains indicate the spatial localization of each region-of-interest.

Figure S4 .
Figure S4.Spatial map of neural coding of (a) the degree of syncopation and (b) groove ratings from 2 Hz neural dynamics.Significant results reported at q < 0.005, FDR-corrected.